1. Field Of The Invention
This invention relates generally to a video tape recorder (VTR) and, more particularly, is directed to a color video signal reproducing apparatus having a color video signal processing circuit for reproducing a picture of high definition.
2. DESCRIPTION OF THE PRIOR ART
When a color video signal is recorded on and/or reproduced from a recording medium, such as, a magnetic tape or the like, by a conventional VTR, a luminance signal and a carrier chrominance signal are separated and then recorded on the magnetic tape in the recording system of the VTR, and the luminance signal and the carrier chrominance signal are mixed or added to each other in the reproducing system of the VTR to provide a composite color video signal. In the monitor or receiver for displaying a color picture corresponding to such color video signal, the color video signal from the VTR has to be separated again into the luminance signal and the carrier chrominance signal so that the signal processing is thereby complicated. Further, there is the risk that the quality of the color video signal will be deteriorated in the course of the repeated separation and mixing together of the luminance signal and the carrier chrominance signal.
In order to avoid the foregoing problems, it has been proposed to employ a VTR with a so-called S (super) output terminal arrangement through which the luminance signal and the carrier chrominance signal are separately provided to a monitor receiver. A reproducing system 10 of such previously proposed VTR for separately providing the reproduced luminance signal and carrier chrominance signal to an associated monitor receiver is shown on FIG. 1 to comprise a pair of rotary magnetic heads HA and HB which alternately scan a magnetic tape T for reproducing a color video signal recorded in successive slant tracks on the tape. The outputs of heads HA and HB are supplied through a playback amplifier 11 to a high-pass filter 12 and a low-pass filter 13 in which the reproduced color video signal is separated into an FM luminance signal Y.sub.FM and a down-converted chrominance signal C.sub.L, respectively. These signals Y.sub.FM and C.sub.L are supplied to a luminance signal processing circuit 14 and a chrominance signal processing circuit 15, respectively. As is well known, the luminance signal processing circuit 14 includes an FM demodulator indicated schematically at 16 for providing a luminance signal Y, and the chrominance signal processing circuit 15 includes a frequency converter (not shown) by which the down-converted chrominance signal C.sub.L is re-converted to a carrier chrominance signal C having the standard carrier frequency f.sub.sc. Further, the chrominance signal processing circuit 15 includes a delay line, as indicated schematically at 17, providing a delay of one horizontal period (1H) and forming part of a comb-filter by which a cross-talk component between adjacent tracks is cancelled. The reproduced luminance signal Y from the luminance signal processing circuit 14 is supplied through a band-eliminating filter or trap circuit 18 having a central frequency f.sub.sc to one inlet of an adder 19. The purpose of the trap circuit 18 is to remove from the reproduced luminance signal Y a noise component near to the carrier frequency of the reproduced carrier chrominance signal C from the processing circuit 15. Such carrier chrominance signal C from the chrominance signal processing circuit 15 is supplied to another input of the adder 19 in which it is mixed with, or added to the luminance signal Y which has had the noise component removed therefrom. The resulting composite color video signal (Y+C) is supplied from an output of the adder 19 through an amplifier 20 to an output terminal 21. The reproduced luminance signal Y from which the noise component has been removed in the trap circuit 18 is also separately supplied through an amplifier 22 to an output terminal 23, and the carrier chrominance signal C is separately provided at an output terminal 25. Such output terminals 23 and 25 constitute the previously mentioned S (super) output terminals of the reproducing system. It will be appreciated that connections may be selectively provided to a monitor receiver (not shown) from either the output terminal 21 or the output terminals 23 and 25 for thereby supplying to the monitor receiver either the composite color video signal (Y+C) or the separated luminance signal Y and carrier chrominance signal C.
In the conventional VTR, the frequency bands of the reproduced luminance signal Y and the reproduced carrier chrominance signal C are selected as shown on FIG. 2 so that the signal components thereof do not overlap each other when the signals Y and C are mixed together to form the composite signal. In such case, the horizontal resolution of the reproduced picture is, for example, about 240 horizontal lines.
Recently, in the course of the development of video technology, it has become desirable to provide a picture of higher definition from a video signal reproduced by a VTR. In order to achieve the foregoing, the carrier frequency of the FM modulator included in the recording system is made higher than that used in the prior art and, as a result thereof, the frequency band of the luminance signal Y is expanded to reach up to 5.0 to 6.0 MHz, for example, as shown in FIG. 3, thereby to provide increased horizontal resolution of the picture with, for example, 400 to 500 horizontal lines therein.
However, if the luminance signal Y has a wide frequency band so that it includes or contains the frequency band of the carrier chrominance signal C, as shown in FIG. 3, a problem arises in the conventional VTR in that the carrier chrominance signal and the corresponding frequency band of the luminance signal interfere with each other when the signals Y and C are mixed in the adder 19. For example, if a Y/C separator circuit included in the recording system of the conventional VTR utilizes a line correlation for recording and/or reproducing a color video signal, the carrier chrominance signal is mixed with the luminance signal and, therefore, the carrier chrominance signal C is reproduced both in the luminance signal system and the chrominance signal system. However, the automatic phase control (APC) is effected only in the chrominance signal reproducing system so that the phases of the carrier chrominance signals reproduced by the luminance and chrominance signal systems, respectively, do not coincide. Thus, when the luminance signal Y and the carrier chrominance signal C are added together, for example, in the adder 19 on FIG. 1, a so-called zero beat interference occurs. Further, that portion of the wide-band luminance signal Y which corresponds with the band of the carrier chrominance signal C in FIG. 3 is mixed with the carrier chrominance signal in the system for processing the latter so that an incorrect color is produced, particularly in portions of the reproduced picture having narrow slant-stripe patterns, that is, so-called cross color interference occurs.